One thing I was wondering was is if it makes sense to reproduce sounds over 20 kHz if you're listening to Red Book. Even if the sounds in the inaudible range can modulate the audible sounds (audibly) in real life, it is my understanding thatred book can not reproduce sounds over 22.05 kHz, in which case the supertweeters would be reproducing either, at best, nothing, or at worst, noise that the CD player didn't filter out. Of course hi rez formats probably wouldn't have this limitation, and perhaps vinyl wouldn't either (can vinyl reproduce sounds in ultrasonic range?) Note that I am not stating this as fact, but a thought that I'm hoping someone with more experoience can comment on.

I have the Townshend Super Tweeter, got them last summer from Max here in the UK. They are incredible. Once you have them in your system, you are hooked. They are smaller than a CD in lenght and about 2" wide,x 4" long, come in chrome. Here is the best thing they have a dial control with 8 increments,on the back.((( I think this is a must.))))) I have mine set at 2, could go to 3 or 4 for classical. I find the setting 2 works with all musik. I have mine sitting on top of my Infinity Preludes that is 57" off the floor not a problem. I did set them at 38" off the floor when I got them , but didn't seem to make a big difference. You will hear music off your cd that will shocked you. All I can say is once you have these little expensive STweeters in your system, just try to turn them off.

I'm not sure who sells this in the US, www.townshenaudio.comIf you get a chance give them a try !

I found the spec sheet , here's what Max says about The Super Tweeter they are designed to extend the responce of conventional HI-FI speakers to 100 KHz, by adding these super Tweeters you will gain the advantage of the extended frequency reponce delivered by the new digital audio formats SACD, ( which I have) DVD-A ,96/24 PCM and DVD-V and to fully utilise the 30KHz plus frequency reponce previously only available from high-quality vinyl reproduction.The low frequency -3db point of the first order crossover is set at 20KHZ. For speakers with sensitivity of 80db to 110 db. I took this off his info sheet.Cheers

Supertweets are great in theory but diificult to implement in practise (to do it WELL, that is -- which you SHOULD do as these tweets are VERY expensive). A few considerations:*time-aligning the tweet to the main spkr: at 20kHz, the wavelength is very small, you're playing with fractions of an inch OR the tweet will out of phase with the rest*relative amplitudes: can you bring the supertweet to the exact amplitude?* Not LEAST: musical info over 20kHz in redbook??? (OTOH you DO have info on LP, and other hi-rez)

Mostly, you'll find that the 1st order x-over has the supertweet simply overlaping with your regular tweet, increasing amplitude in the 5-15kHz region (with some distortion). You can do the same with a regular (i.e., cheaper) tweet...But I agree, the idea of having response up to 100kHz is beguiling!

Having heard plenty of ML's (although not the CLS, but I don't think it's an exception), I don't agree that they can't benefit from a supertweeter. Many speakers have a more extended and airy treble than they do. I'm speaking as a current owner of ML products.

that said, Gregm's points are worth thinking about; it would not be easy to time align the ST and bring it to the exact amplitude you need.